Ben Hogan, Lee Comeaux, and the Right Hand Hit

Dave Tutelman  --  November 27, 2010

Ben Hogan advocated hitting with the right hand (even both hands) at impact. Recently, Texas instructor Lee Comeaux has been teaching his students a "right-hand slap", which seems very Hogan-esque. One of his students, who has seen marked improvement in his distance, asked me to investigate the physical basis of the improvement. My brief study concludes that it's not what the proponents believe, and the extra distance might not have any explanation in simple physics. Hitting with the hands at impact produces no additional clubhead speed -- none. That might not prevent it from being effective instruction, though.

A Little Background

Before I start, let me apologize to my left-handed readers. Hogan and Comeaux use 'right' and 'left' in describing a right-handed swing. I will follow suit. You lefties will have to mentally transpose. (It's not that I don't sympathize; my own son is left-handed. But trying to accommodate it in the wording gets very clumsy.)

Golf Swing Physics

 Before we go on to analyze the slap swing, let's review what we know about the physics of the swing. The illustrations are taken from my tutorial article on golf physics. For more detail than is given in that article, see Rod White's article. For more detail on the mathematical model used to analyze the swing, see my article on the double pendulum. The golf swing is analyzed by physicists as a double pendulum. The inner member of the double pendulum is the triangle of the shoulders and the two arms (green in the diagrams). The outer member is the club itself (black in the diagrams). The variables in the analysis are the lengths of the two arms, and the forces on them. Well, not exactly forces; they are turning forces, more precisely known as "torques". (1) The body rotation exerts a torque on the shoulders, which turns the shoulders and arms. (2) The forearms, wrists, and hands might exert a torque on the club via the grip. If you are not certain you understand the model, its applicability is discussed in more detail in another of my articles. In particular, you may be concerned that the role of the hips or the right arm might not be properly modeled if this is my tool for analysis. You would be right to be concerned. But whether that concern will doom the analysis is a different story. So understand that article before you dismiss the results out of hand. The most notable of the analyses using the double pendulum model is that by Ted Jorgensen ("The Physics of Golf"). He, and just about every other engineer or physicist who has studied the swing, has concluded that the basic efficient swing is one that depends completely on body rotation (shoulder torque), and lets the wrists hinge freely (that is, zero wrist torque). In other words, you get a very efficient swing from turning the body and allowing the inertial forces on the club to cause the release. (Those inertial forces are usually referred to as centrifugal force. This is a vague and undisciplined use of the language, but we'll stick with it unless the distinction needs to be made for pragmatic reasons.) Hitting with the hands constitutes the addition of wrist torque late in the downswing. This is the basis of our physical analysis of the Hogan and Comeaux swings.

What It Might do

I used three distinct approaches to determining the value of adding wrist torque late in the downswing:
1. Stand on the shoulders of giants. Specifically, see what people concluded who had seriously looked at the problem before.
2. Try it myself. Of course, this will only be anecdotal -- hardly a controlled scientific experiment. But it will give me a feel for how the swing works, an insight into the analytic results, and ideas for what to try next.
3. Do the math. I used a computer program that simulates the swing, where the torque profiles can be varied over the downswing.

Shoulders Of Giants

• Let's start with Rod White's analysis. He devotes a subchapter to what happens if you add wrist torque to the standard swing. The graph he presents is unequivocal. Positive wrist torque (torque to uncock the wrists) results in less distance, not more. It may seem paradoxical, but that's what physics says. It is worth noting that negative wrist torque (to hold the wrist cock angle) results in more clubhead speed and more distance.

• Tom Wishon has been the Chief Technical Officer of Golfsmith, and now has his own golf club component company. His company is recognized as an innovator, and he is the world's foremost advocate of custom fitted golf clubs. In his book "Common Sense Clubfitting" (chapter five on shaft fitting), he writes:
"The condition of the shaft being slightly bent backward with the head lagging behind the shaft is very rare in the game. This is because the swing skill plus strength that is required to maintain radial acceleration and the wrist-cock angle until very late in the downswing is such that very, very, VERY few golfers can do this. Far more common are the conditions in which the shaft arrives at impact either straight or slightly bent/curved forward with the head in front of the forward curve of the shaft."
In other words, it takes more athletic ability than almost anybody possesses to apply a positive wrist torque late enough in the swing to be helpful. (If I may add my own opinion, not Wishon's words: It isn't just strength; it's also speed. Late in the swing, centrifugal force is whipping the clubhead toward impact. The wrist-cock angle is being dragged out very fast, so it takes a lot of hand speed to even keep up, much less help it along.) One other thing he mentions: we can tell if the wrist torque is negative or positive on the basis of shaft bend. That is important, and we will come back to it later.

• Jorgensen's book is a bit more optimistic. In his chapter 4, some of the points he makes are:
• It is always a bad idea to apply positive torque early in the downswing.
• It is always a bad idea to apply positive torque throughout the downswing. (We knew that already from Rod White.)
• It is generally helpful to apply negative torque (that is, hold the lag angle, retard release) throughout the downswing. (Also Rod White.)
• What is new and interesting is his analysis of adding positive torque late in the downswing:
"Let us look at such a helping action of the wrists late in the downswing. Extensive calculations with the standard swing modified by a constant helping torque of 2 ft-lbs by the wrists late in the downswing show that indeed such a helping torque does produce an increase in clubhead speed at impact. The maximum increase in clubhead speed at impact comes with the torque starting about seven hundredths of a second before the ball is hit. The resulting clubhead speed was found to be only about 0.7% greater than that of the standard swing. This constant torque acting for a longer time or for a shorter time at the end of the downswing produces clubhead speeds less than the maximum."
In other words, there is room for a properly executed push or slap to increase power. But it is not much of an increase, and it has to be timed very precisely. Not extremely promising, but not a closed door either. The other giants didn't offer any hope at all.
So we have found a general consensus among those who have investigated the swing mathematically:
1. A strong shoulder turn increases clubhead speed. (The model does not say whether the turn should be a product of the shoulders, the torso, the hips, the legs,... Just that a strong turn powers the swing well.)
2. Wrist torque that helps release usually winds up hurting clubhead speed at impact. You may get higher clubhead speeds earlier in the downswing, but those speeds don't hit the ball; by the time of impact, the clubhead speed is lower than with no wrist torque at all.
3. Wrist torque that retards or delays release usually winds up increasing clubhead speed at impact. #2 and #3 are recognized as paradoxical, but they work time and time again on the computer -- and also on the driving range.
4. When it comes to a "pulse" of helping torque just before impact, there is no consensus. Jorgensen found there is some small advantage to be gained. Wishon believes it is nearly impossible for a real, live human being to achieve that gain. And White didn't even look at the question. (We will look at it a bit later.)
Before we move on, let's take a look at why helping (positive) wrist torque hurts the ultimate clubhead speed, while retarding (negative) torque increases clubhead speed. Here are three "strobe view" simulations of the swing for us to compare. When viewing them, bear in mind that the release is powered, at least in part, by centrifugal force -- and centrifugal clubhead acceleration depends on:
• Rotational speed. The faster the golfer rotates, the more the force.
• Wrist cock angle. The more acute the wrist cock angle, the more the centrifugal force is contributing to clubhead speed, by throwing the club outward. Conversely, the more the wrist cock is already released, the less the clubhead can be thrown outward (accelerated) by centrifugal force.
Of course, body rotation is faster later in the downswing. So we can get the best acceleration from centrifugal force if we hold the wrist cock angle until late in the downswing when fast rotation does the most good. Let's look at the pictures:

 No wrist torque (the "standard swing") Release is driven only by centrifugal force in this swing.. Maximum acceleration is 60msec before impact. (The red-dot clubhead is the point of maximum acceleration.) Positive (helping) wrist torque Maximum acceleration is early, 80msec before impact. Very little wrist cock is left late in the downswing, stealing centrifugal acceleration. The clubhead positions are closer together at impact, indicating less clubhead speed. Negative (retarding) wrist torque Maximum acceleration is late, only 40msec before impact. Wrists stay cocked late into the downswing, encouraging centrifugal acceleration. The clubhead positions are farther apart, indicating more clubhead speed.
(The pictures were generated by the SwingPerfect computer program. We'll be using it more in a later section.)

One interesting observation: Jorgensen found that "late wrist torque" should be applied to a "standard swing" beginning "seven hundredths of a second" (70msec) before impact, and continuing through impact. That corresponds almost exactly to the point of maximum acceleration. So his conclusion might be restated, "As long as inertial acceleration is increasing, don't mess with it. Once it starts to fall off, you might help it along with wrist torque." That actually makes sense!

Tried It

I took it to the practice field and then the course. It integrated more quickly and easily than I expected. I've been using it for a couple of weeks, and every round is the same experience. I hit a bunch of really bad shots early in the round, then find my [new?] swing and hit some very good shots. Some shots are significantly longer than I am used to; I have to believe the new swing has something to do with it.

Specific things I have observed while integrating a push/slap.
• It is not a silver bullet. It only works if my fundamental swing is sound. Any faults in the basic swing seem to be magnified by the slap.
• If the slap is introduced early, some very bad results occur. The most common and worst result is a seriously left hit. The ball flight indicates a closed face. This makes some sense, since the slap includes a rotation of the club. Early slap means early rotation, which means rotated past square at impact.
• Even many of the good impacts were pulls or even pull-hooks. That means a closed face at impact.
• I started by thinking of it as a slap or throw with the right hand. Lee Comeaux has a video that describes the move as, "Right hand closest to the body starting the downswing. Right hand farthest from the body through impact." This was a reasonable visualization, and did help.
• Practicing with it for a while, my body was telling me that an energetic straightening of the right arm was the real driving force behind the motion. A little thought told me that both motions had the same effect on the double pendulum model; they added positive wrist torque. (See my article on the double pendulum and the right arm to see why.)
Every round I have played since adopting the motion has included at least one shot that I didn't know I had in me. So it is doing something good. As noted before, this report is anecdotal, not scientific. But it is encouraging, and adds some urgency to find out why it works. Some possible explanations:
• Is it physics? We'll do some modeling and other investigation to find out why.
• Is it biomechanics or kinesiology? Sometimes a swing key has no good explanation in physics, but encourages other good things to happen in the swing. One example: "Accelerate through the ball." Physics says that acceleration makes no difference once the clubface reaches the ball. But experience shows that a body that expects to accelerate through the ball does a bunch of other things right.
• Is it the placebo effect -- or, more accurately, the "Hawthorne Effect"? This ain't just physics; it's human experience. Note that we need to treat any swing experiments as human factors experiments, not physics experiments. The Hawthorne effect comes from an experiment by Western Electric in the 1920s, where they changed things like the lighting in the Hawthorne, Illinois factory to see what effect it had on productivity. Turns out anything they did improved productivity. More light? Productivity went up. Less light? Productivity went up. The fact that they were changing things and watching results was more important than exactly what it was they were changing. The "takeaway" for golf: Consistent attention to one thing -- almost anything, as long as it's not actually detrimental -- is going to help your golf performance. It's called disciplined practice.

Do The Math

OK, time to do the math. Fortunately, I don't have to do it by hand. I have Max Dupilka's SwingPerfect program, which simulates Jorgensen's model of the swing. You can even control the profile of the torques, varying it over the duration of the swing -- both shoulder torque and wrist torque. We are going to use it to see what effect we get from a helping wrist torque late in the downswing.

Here is a screenshot of what SwingPerfect looks like on my computer. It shows both the main window and the controls to set the wrist torque by 20-millisecond intervals during the downswing. There are also controls for the shoulder torque during the downswing and lots of other physical parameters: the golf club dimensions and weights, the golfer's relevant dimensions and weight, and properties of the computation like how frequently to calculate a new point in the downswing.

Note for the use of SwingPerfect

If you're not going to actually do studies using SwingPerfect, then you can skip this note altogether.

Most studies that are good golf science will be variational studies. That is, you are not looking for absolute numbers but rather, "What happens when I change this parameter by that amount?" So want to set it up before the variations are introduced so that:
• The swing is as realistic as possible for the class of player you are trying to simulate.
• Small variations in parameters give small variations in the answers, related only to your parameter variations and not to any artifact of the way you do simulation.
(1) The most important hint is to reduce the time interval to the minimum the program supports, a half millisecond. This greatly improves the accuracy, as well as the stability of the answer in the face of small variations. It will not give as pretty a display, because the strobes are only a half-millisecond apart, but the numerical answers are much better.

(2) In the earlier pictures illustrating centrifugal acceleration, I ran the swing without "Lateral Acceleration" (see Physical Parameters, page 3, in the program) to keep the diagram simple. But a more realistic swing would have lateral acceleration turned on, and that is how I did the numerical studies that follow.

(3) For most of the parameters, I used the default values. I changed the club parameters to reflect how drivers are different in 2010 from what they were in 1999 when Max wrote the program. I used club length = 45", head weight = 200g, and shaft weight = 65g. I also made sure the initial arm angle and wrist cock were 180º and 90º, which is about what most decent golfers do.

(4) One final note: Jorgensen uses the opposite sense of plus and minus for wrist torque. SwingPerfect follows the Jorgensen definition. I chose the "wrong" sense for my narrative in this article. Mine is "wrong" to do the math, but makes more sense when talking to golfers who aren't going to look at the differential equations. So, if you're using SwingPerfect, what I call "positive torque" is minus, and vice versa.
OK, let's compute the effect of a swing with no wrist torque until very late in the downswing; Jorgensen says the last 70 milliseconds helps, and any earlier hurts. So we will try swings with zero wrist torque (the "standard swing"), and a few different helping torques for the last 70msec and the last 110msec. The torques we will try are:
• 2 foot-pounds. Jorgensen used this number, and thought it was quite a lot. I'm not sure it's so big, but perhaps he's right.
• 5.7 foot-pounds. Rod White thought that 10% of the shoulder torque was kind of an upper limit on the wrist torque a golfer could apply. I tend to agree. The default shoulder torque for SwingPerfect is 57 foot-pounds, and 10% of that is 5.7 foot-pounds.
• 12 foot-pounds. Suppose the golfer were actually able to convert all the shoulder torque into arm-piston force (instead of triangle-turning force). This is clearly an upper bound on the wrist torque, and unrealistically high. But let's compute it just to see what could happen. I used a shoulder width of 24" (exactly 2 feet) and a maximum distance between the hand pressure points (using a 10-finger grip) of 5". 57 ft-lb divided by 2ft gives 28.5 pounds of force in the arm piston. Applied over a 5" grip spread, this is 12 foot-pounds of torque.
Here is a chart of the results. The entries in the chart are:
• Clubhead speed, in mph. (Black on white)
• Clubhead speed compared to standard swing, in percent. (Red on white)
• Wrist cock angle at impact, in degrees. (Black on yellow)
 Size of helping torque Zero wrist torque ("Standard Swing") Helping torque starting 70msec before impact Helping torque starting 110msec before impact 2 ft-lb (Jorgensen) 108.7mph 109.3mph (+0.6%) 108.4mph (-0.3%) 8.8º 4.8º 3.0º 5.7 ft-lb (White) 108.7mph 110.3mph (+1.5%) 108.3mph (-0.4%) 8.8º -1.6º -7.5º 12 ft-lb (Full arm piston) 108.7mph 113.3mph (+4.2%) 110.8mph (+1.9%) 8.8º -14.5º -28.6º

Before you talk about how much there is to be gained at 12 foot-pounds, let me remind you that 12 ft-lbs is a theoretical upper bound. You're not going to get anywhere close to this number. It is based on converting all the shoulder torque into wrist torque. I went back and used SwingPerfect to simulate that more accurately; I reduced the shoulder torque to zero when the wrist torque kicked in. When you do that, the clubhead speed drops to 97mph, and the wrist is cupped about 60º at impact. That's a recipe for total disaster; don't even think about it.

So lets consider the first two rows only, to see what might happen with added wrist torque.

First clubhead speed: There's perhaps a couple of miles per hour of clubhead speed to be gained. That translates into no more than five extra yards -- certainly not enough to explain the 30-yard gains Rock reports. Not only is the gain pretty small, but the slap has to be timed very precisely! If you start the slap 40msec earlier than you should, you lose the whole gain and then some.

Next wrist cock angle: The standard swing has a slightly bowed wrist at impact, with 8.8º of wrist cock angle remaining to be released. As you crank in helping torque, you decrease the wrist cock angle. If you crank enough wrist torque to make a noticeable difference in distance, the wrist angle at impact becomes somewhat cupped. Because this change is due to a rotation of the forearms, the result is a clubface pointing more to the pull-hook side than usual. Whether it is a pull-hook or just a pull depends on what adding the torque does to your clubhead path; that's swing mechanics that the double pendulum does not address. But there is no doubt that the ball will go left of where it would go with the standard swing, unless you do something else to counteract it. And indeed I experienced that in practice.

I did one more mini-study with SwingPerfect. Because of things discovered later in this article, I wanted to answer the question:
Suppose the golfer is exercising retarding torque for most of the downswing. We know this produces more clubhead speed. But... Would releasing this negative torque just before impact increase the clubhead speed further?
This would appear to be reasonable, in light of the numbers above, so let's check it out:

 Case Clubhead Speed Wrist Cock at impact Standard Swing (no wrist torque) 108.8mph 8.8º 2 ft-lb of negative wrist torque 114.5mph (+5.2%) 17.6º 2 ft-lb of negative wrist torque, released to 0 at 70msec 114.7mph (+5.4%) 14.2º 2 ft-lb of negative wrist torque, released to 0 at 110msec 113.4mph (+4.2%) 12.3º

This tells us that negative wrist torque is a good thing for clubhead speed. By itself, it gives more than a 5% increase in clubhead speed, enough for a gain of about 17 yards. We knew it would give us an improvement, but that's big.

Releasing that negative wrist torque 70 milliseconds before impact buys us a tiny bit more clubhead speed -- but not enough for even one more yard. Definitely not worth learning. And if you do your release too early, you lose that gain and a lot more.

What It Doesn't Do

So far, we have found out that a right hand hit or slap is modeled for analysis purposes as a wrist torque introduced very late in the downswing. If it is applied for the last 70 milliseconds of the downswing, we may see a small increase in clubhead speed. Not enough for an extra ten yards, but probably a measurable increase. It must be applied at a precise time; much earlier than 70 msec does more harm than good, and much later just doesn't help.

So is that the mechanism for the increased distance experienced by users of the right-hand hit? Is there an objective way to find out?

It would almost seem foolish to ask this question. There is no doubt in the minds of those who swing with a slap that they are pushing the clubhead through impact. But we cannot dismiss lightly Tom Wishon's admonition that almost nobody can keep up with the releasing clubhead well enough to supply additional acceleration to the clubhead with the hands. So let's see if we can verify that the positive wrist torque is actually being applied to the grip.

Shaft Bend

It turns out there is a way to find out whether the slap actually causes a positive wrist torque. We just look at shaft bend. But first we have to understand shaft bend.

The shaft is a spring that transmits wrist torque from the grip to the clubhead. If you bend the shaft, it transmits a force to the other end that tries to move the object there. Specifically, it tries to move it in a direction to straighten the shaft. That's what any spring does -- apply a force so it can get back to its "resting shape". (Just a reminder: we are bending the shaft in flex, not around its axis -- what shaft specs refer to as "torque".)

During the downswing, three conditions can prevail: a straight shaft, a shaft bent backward, and a shaft bent forward. All three show up at one point or another. Let's look at the three conditions:

 Straight shaft - If the shaft is straight, that means it is conveying no lateral force to the clubhead. The hands are not applying a wrist torque to the grip, neither to accelerate nor decelerated the clubhead. For the standard swing with freely hinging wrists, the shaft would find itself straight once the wrist cock angle "left the stop". So why is there shaft bend in almost every swing we see, and long after the wrist cock starts to release? The most important reasons are: Not many players keep their wrists as frictionless hinges. They will exert some torque, whether they are trying or not. Because the center of gravity of the clubhead is not in line with the centerline of the shaft, the centrifugal tug of the clubhead will bend the shaft a little bit. There is certainly bending early in the downswing, where the "stop" of the standard swing is applying torque. Some "rebound" from this initial bend may occur. But, if the wrists were truly hinging, then this effect would be small and short-lived; it would be long gone well before impact. Bent backward - If wrist torque is accelerating the clubhead toward the ball, then the shaft will be bent backward. That is the only way that the spring of the shaft can apply a helping force to the clubhead. Remember, the force will be applied in a direction to straighten the shaft. So a shaft bent backward -- the clubhead trailing the grip -- is a sure indicator of a positive or helping wrist torque. Bent forward - By the same reasoning, a forward shaft bend shows a negative, or retarding, wrist torque. Again, the force applied by the shaft is in the direction to straighten the shaft. The force applied to the clubhead by a forward-bending shaft is slowing the release of the clubhead. A little bit of forward bend in the vicinity of impact may be due to the clubhead's center of gravity. But that will seldom be as much as an inch of bend, and most swings have a lot more forward bend than that coming into impact.

How Right-Hand Slappers Bend The Shaft

This is all very interesting, but how can we use it to learn about the right-hand slap? Let's go to the videotape! (Always wanted to say that, even though these days it's an MPEG file or YouTube page, not a tape at all.) I have face-on videos of several golfers that purport to do a right-hand slap, including Lee Comeaux and Ben Hogan. Let's look at freeze-frames near impact. We'll see how the shaft is bent, and deduce from that whether they are actually applying a helping torque.
Note: The shaft bend in some -- but not all -- of the following pictures may be an "optical illusion". Many digital cameras and camcorders suffer from a photographic distortion that may exaggerate shaft bend, or even create bend where there isn't any. I have tried to point out the pictures where this might be a problem. To understand the problem yourself, read my article on Focal Plane Distortion.
Let's start with some frames of Lee from the video we pointed to earlier.
 Lee starts down with the wrists well-cocked. The backward bend of the shaft at this point of the swing is typical, and represents the "stop" that keeps the wrist cock from collapsing inward. Here centrifugal force has taken over, and is trying to uncock the wrists. Lee claims to be doing a right-hand push at this point, but the shaft bend clearly indicates that the hands are actually opposing the uncocking, not causing it. (In all likelihood, this picture is not affected by focal plane distortion. It reflects what the shaft is actually doing.) At this point, the ball is gone. With most swings I've observed, the shaft would be bent backward, at least near the tip, in reaction to impact with the ball. The fact that Lee's shaft is still bent well forward suggests that the clubhead came into impact bent well forward -- with the clubhead's considerable momentum still pulling the hands through -- and impact caused only partial recovery. (The forward shaft bend in this picture may well be exaggerated or even caused by focal plane distortion.)

In Hogan's peak years, slow-motion video was not nearly as good as today. In spite of the ample footage of Hogan available, very little is of high enough quality to look at shaft bend. But I did find one clip on YouTube good enough to try to draw some conclusions. Here are a couple of frames from that clip.
 Fairly late in the downswing, the bright steel shaft is clearly bent forward. If Hogan was able to "hit the ball hard with both hands", it kicked in later than this. Our analysis says that is too late to help clubhead speed measurably. It is hard to see the shaft in this frame; remember what I said about video quality from Hogan's heyday. But, if you can make out the blur that is the shaft, you can see it is still bent forward. No hand-hit working here, only a few milliseconds before impact.

If you want a couple more pictures of shaft bend, I had two of Lee Comeaux's students, Rock (left) and Karl. I have removed the picture of Karl, because the focal plane distortion was so large it was hard to tell what the shaft was doing.

In Rock's case though, there is a clear forward bend even with the fast shutter. The picture was a couple of milliseconds before impact. Any hand hit he can introduce after this does not have enough time to change the clubhead speed.

Both Rock and karl showed very good swings, and they have a lot of power. Both these golfers credit Lee Comeaux with adding power to their game. But we see here that, whatever is causing their improvement, it is not because the right hand is pushing the clubhead through impact. Physics says that just isn't happening.

How Top Golfers Bend The Shaft

We have to be careful about using photography to measure shaft bend. There is, of course, focal plane distortion; we've already mentioned that. It is also worth noting that the best measurements of what we are looking for come with the camera perpendicular to the swing plane. You can draw reasonable conclusions from less careful face-on views, but for accurate measurement the position of the camera is important.

But there are better ways to measure it. In the 1990s, TrueTemper had an instrument they called ShaftLab, which measured shaft bend directly. They attached strain gauges to the shaft of an actual club, and transmitted to a computer samples of the shaft bend during the swing. I have an article describing in detail what we can learn from the ShaftLab data published by TrueTemper.

Let's review one specific lesson: the fact that the shaft is always bent forward at impact, and for tens of milliseconds before impact. Here is a scatter plot for shaft bend at impact; it reflects the swings of nine PGA Tour pros from the 1990s. Impact always has leading and toe-down bend. Moreover, it is leading by more than can be explained just from centrifugal bending -- that is, radial acceleration pulling on the center of gravity (CG) of the clubhead. There is bending due to dynamic forces of the swing.

In fact, a leading bend at impact says that the head is pulling the hands through, so the hands must be exerting torque that resists the release of the club. If the hands were exerting releasing torque, then all those dots would show lagging bend, or at least be positioned to the left of the white "CG" line.

For those who feel that Long Drive competitions change the rules, physics included, here's Jamie Sadlowski just before impact. (Jamie won the ReMax World Championship the past two years running, and won handily.) Yes, his shaft is clearly bent forward, telling us he gets his distance from his huge body turn in the backswing, inhuman wrist cock, and holding that wrist cock very late into his downswing -- and not from forearm or hand strength driving the clubhead through the ball.

Likewise for Tiger Woods, as if there were any doubt.

(Both these pictures are probably unaffected by focal plane distortion. The shaft bend is real. The Sadlowski picture was taken by Rick Malm using a technique designed to minimize distortion. The technique is explained in the article. The picture of Tiger is a frame from the super-slow-motion video used in a well-known Nike ad a few years ago; the camera scan rate is very fast, which minimizes distortion.)

Why?

Ben Hogan is convinced that hitting the ball with his hands is a big source of his power. Rock and, to a lesser extent, Lee Comeaux lean toward that opinion as well. They have worked and practiced to make it happen. They can feel it happening. But the physics and the videos say that the clubhead is pulling the hands into the ball; their hand-hit is not accelerating the clubhead. What is going on here?

My take on Tom Wishon's statement is the key. If you try to add wrist torque late enough in the swing to help (the last 70msec before impact), the hands just can't keep up. Centrifugal acceleration is turning the hands so fast that the wrist muscles and right-arm piston can't turn the hands as fast as the club is already turning them. And if the muscles can't make the hands exceed what the club is doing, then they can't add any acceleration to the clubhead.

What It Probably Does

Expecting a right-hand slap or late push to give more distance does not have any basis in physics. We know that now. But there is a substantial body of anecdotal evidence that says it works. Most notably, Hogan won a lot of tournaments with a swing intended to do that (even if it in fact did not do it).

Why does it work? We have ruled out physics. I think we can rule out the Hawthorne effect. True, a lot of practice of any swing that is not seriously flawed is going to improve your game. But I, for one, saw results in the first round I played with it, after only two practice sessions. So something is going on there besides just practice.

Let's mention some of the possibilities, without evaluating them -- yet. I am beginning a study in conjunction with Lee Comeaux to try to determine what is really going on.
1. Something about the motion encourages some other good habit. This might result in more shoulder torque or a later release, or perhaps something else.
2. Following up on the first point, it might be that focusing on forcing a 90º release just before impact causes the golfer to hold the 90º lag until just before impact. That synchronizes the release to when it should be, and perhaps causes the golfer to exercise negative wrist torque earlier, in order to hold the lag until very late in the downswing.
3. A related possibility: Anybody who has played ball-and-stick sports other than golf has learned to depend on hand action to supply power. You need it in baseball, stickball (I grew up in the Bronx), tennis, etc. For someone like that, it's very hard to train your body and your subconscious to swing through impact with passive hands (the "standard swing"). If you use a late right-hand slap it might not help, but at least it won't hurt if it's late enough. So the slap swing acts as permission to let the hands get involved, in the least harmful way. If you had been allowing the hands to get in the way by releasing early, then the slap move might cure the problem. If this is the answer, the slap move is not so much a powerful move as an antidote to something you are doing that loses power.
4. An aggressive move through the ball -- like the slap -- might be encouraging a strong, committed follow-through from a golfer who normally gives up the swing after impact. (That is sometimes a problem of mine, but not so much since I started using the slap motion.)
5. Or it might be something completely different. Lee's swing involves a lot more than just the right-hand slap, and those who have been practicing everything Lee teaches report big improvements. I started out suspecting his other advice was in support of the slap, and didn't get very deeply into them. But I have talked with Lee, and there are lots of other things he teaches that could have value in their own right. So maybe one or more of these, and not the right hand slap in the impact area, is responsible for the improvement.
In any event, Lee and I are going to see if we can apply physics to other parts of the golf swing that he teaches.

Summary

From time to time, someone comes along advocating a hit with the hands in the vicinity of impact. Hogan was very explicit about it, and Lee Comeaux is a proponent these days. This study has determined that such a move does not by itself increase clubhead speed. The steps that led us to this conclusion were:
• According to physics studies using the double pendulum model, it was determined that small improvements in clubhead speed could indeed be achieved by adding helping wrist torque late in the downswing. But it has to be added about 70 milliseconds before impact; any earlier hurts clubhead speed more than it helps, and any later and the force isn't there long enough to have a significant effect on clubhead speed. These facts have been reported by previous investigators and confirmed by our analysis.
• We looked at frames of videos of golfers who claim to use a right-hand hit. Wherever we saw the shaft just before impact, it was always bent forward. That means that, whether the golfer thought so or not, the slap was not applying any accelerating force to the clubhead.
• We also looked at video frames and ShaftLab traces of PGA Tour pros and Long Drive competitors. They also showed a forward bend, meaning a resisting torque rather than an assisting torque.
• The reason would appear to be that the grip is rotating too fast approaching impact, due solely to centrifugal acceleration. The golfer's hands cannot move fast enough to catch up to the grip and apply pressure to it.